Open source project to develop geopolymer cast stone construction

Historical Cast Stone Formulas

This report by Professor Miles Lewis on historical cast stone formulas is one of the more interesting papers I’ve read lately. A big thanks to (???) for sending it to me. It helped me realize people have been pursuing the same dream we have here for many years – to create cast stone out of low cost, locally available materials. And while you’re reading keep in mind that even moderately successful formulas may prove useful to some readers. A few quotes are listed below.

– Major Mitchell noted that a very hard mortar for use in pointing might be made by adding coal ashes and iron filings, or the sweepings from a forge.
– A later French type, known as Sorel stone, was made by calcining magnesite and mixing it with sand or powdered marble, wetting it with a waste liquid from saltworks, which contained magnesium chloride, and stamping it into moulds.
– in 1859 Joseph Sullivan won a prize offered by the Melbourne City Council… [for his] Improved Artificial Stone, which surpasses in durability and appearance any yet
produced; it is of a light tint and requires no painting or colouring, and is equal to the finest Portland: exposure to the atmosphere gives to the composition the hardness of granite, improves the colour, and renders it quite impervious to damp; it is not affected by the most severe frost or heat
– The most widely advertised and possibly the best known artificial stone of the period
was not based on cement at all. It was patented in England in 1844 by Frederick
Ransome, the inventor of the equally well-known silicate indurating process. It was
made by cementing broken or pulverised stone with a solution of silica in caustic
alkali – that is, water glass – and moulding it under pressure to produce a dense
compound suitable even for grinding. It had a crushing strength of about 64 to 73 MPa, which was 800% stronger than Caen stone and nearly 25% greater than Darley
Dale stone, one of Britain’s toughest freestones. As ‘artificial silica stone’ in the
forms of urns and a balustrade it won a gold medal for Ransome & Parsons at the
Great Exhibition of 1851.
– An artificial stone patented in New South Wales by Nicolle and Mort of Sydney – presumably before 1877, as the patent had expired by 1891 – was made by mixing sixty parts of clean sand, eight of aluminium silicate; four of lime, and one of hydraulic lime.
– Edmund Coignet took out a French patent in 1859 for a béton in which lime, sand and water were mixed into a grout and poured over gravel. First he defined common béton, which was a mixture of sand, pebbles, broken stones, common lime and water, except that hydraulic lime was used where it was for marine purposes. Béton-coignet, in contrast, was an ‘artificial stone’, and consisted of sand, lime and water – that is, no coarse aggregate.